A licensed spectrum is a wireless spectrum granted to an operator to use according to laws and regulations of each country, and only a wireless spectrum that has a license and authorization and that passes a network entry tested and is licensed can be used. However, an unlicensed spectrum, for example, a working frequency band of a device such as a WiFi device or a Bluetooth device, can be used without being authorized by a government. Because licensed spectrum resources allocated for mobile communications are exiguous, which limits a future development scale of a mobile communications network, currently, combining licensed spectrums with a great number of unlicensed spectrums is taken into consideration, so as to improve a transmission capacity of a mobile network. According to statistics, currently, in the 5 GHz frequency band, a sum of unlicensed spectrum resources that has been allocated in all the countries around the world may exceed 500 MHz, and mobile communication device manufacturers and mobile network operators pay attention to these unlicensed WiFi spectrums, so as to derive solutions such as the LTE in unlicensed spectrum (LTE-U), and currently, announce that testing projects on the LTE-U would be carried out. A License Assisted Access (LAA) technology that is currently actively researched by the International Organization for Standardization 3GPP is a typical solution of expanding a capacity of a mobile communication system by using unlicensed spectrums, in which a transmission capacity of an LTE system is further improved by allowing the LTE system to use unlicensed spectrums.
In an LAA system, a base station may improve user throughput and a system capacity by using unlicensed spectrums. However, because the unlicensed spectrums are shared among multiple systems, to enable the systems to have fair opportunities to access the unlicensed spectrums, a conventional contention mechanism is generally used to determine use of the unlicensed spectrums. Uplink scheduling of the LAA system is used as an example, and a relatively mainstream implementation method that is currently proposed is: the base station first schedules some user equipments (UEs) at a scheduling moment and determines information such as time frequency resources occupied by users and transmission parameters (for example, transmit power, a modulation and coding scheme, and a data block size) in a scheduling instruction (UL Grant), so as to instruct the user equipments to prepare for uplink transmission. However, because fair access to a spectrum needs to be implemented with another coexistent wireless system (for example, an 802.11 wireless local area network system) in the unlicensed spectrum, a competitive channel access mechanism is used. Therefore, at a scheduling moment when the base station schedules uplink transmission of a user in the unlicensed spectrum, it is impossible to determine whether the user equipment can successfully obtain the channel by contention at an expected uplink transmission moment after several sub-frames (for example, for an LTE Frequency Division Duplexing (FDD) system, the fourth sub-frame following the current sub-frame). When the base station schedules uplink transmission of a specific user on multiple unlicensed carriers at the same time, the user equipment may possibly not obtain a channel on some carriers by contention to cause that transmission cannot be carried out. In addition, because some transmission parameters on each carrier have been specified by the base station in advance, waste of some transmission resources (for example, transmit power) of the user equipment may be caused, thereby reducing flexibility and transmission efficiency of the LAA system.